The present invention is related generally to digital data transmission protocols in communications networks and, more particularly, is related to efficient, reliable packetized digital data transmission protocols for improved transmission performance with reduced bandwidth requirements in networks which are low quality or have widely varying physical channel performance, such as, for example, wireless network environments.
In a typical Open Systems Interconnection (OSI) reference model network protocol, several layers are defined and dictate the protocol stack. A particular OSI model protocol that is commonly used for communications networks, including the Internet, is the Internet Protocol (IP), and particularly the supplement IP known as the Transmission Control Protocol (TCP/IP). In all OSI model protocols, including IP and TCP/IP, a higher level layer, e.g., a transport protocol layer, communicates packetized data to an underlying level layer, e.g., an Internet protocol layer. Subsequently, the underlying level layer, e.g., the Internet protocol layer, eventually relays the data to a data link layer, which in turn relays the data to a physical layer, which then directs the physical transmission of the data.
For example, in such communications, first, data meant for transport by a network device is formatted according to the OSI model data protocol, containing several defined layers, such as physical layer, data link layer, network layer, transport layer, and so forth. An illustration of such an OSI model protocol is given in FIG. 1. In the model of FIG. 1, data for transmission by the device is first processed by a transport layer; this transport layer can be overlain by an application layer, specific to the particular application. Typically in the transport layer, the transport mechanisms are defined such that the data is partitioned into data packets for later physical transport.
The data from the transport layer is then processed by an interconnected network layer. An example of this network layer is the conventional Internet Protocol (IP) layer, as widely implemented today in TCP/IP networks, such as the Internet. The interconnected network layer prepares the packets from the transport protocol layer for transport across interconnected networks.
Next, the data link layer prepares the data for physical transport across a defined network physical channel, such as an Ethernet link or other type of local area network.
Finally, a physical layer performs the actual transmission of the processed data to and across the network operating under the particular OSI model implementation.
Presently, one of the most common implementations of the OSI model in network communications is TCP/IP. For example, Internet communications are typically conducted according to TCP/IP, and this is considered the standard for the Internet. In TCP/IP, the physical layer remains a constant and is independent of the devices or network, so long as the devices and network are capable of using the OSI model layers in accordance with TCP/IP.
In TCP/IP, the network layer is IP and the transport layer is TCP. IP and TCP are each well known and defined as standards. Under the standards, the IP portion of the protocol takes care of routing data packets to the intended destination. The TCP part performs integrity checks on the data and enhances reconstruction of the packets into the original message or file at the destination end.
Although TCP is presently widely used in data communications, including over the Internet, the protocol was designed primarily for use over reliable and non-variable channels and bandwidth, i.e., primarily wired connections. The shift in direction of communications to mobile and wireless devices and communications, thus, was not a premise on which the TCP protocol was defined. The premises and assumptions on which TCP was designed no longer have the same application in the wireless world and as other and newer lower quality and variable channel networks evolve.
There is, therefore, a need for improved protocols and methods that account for the characteristics of wireless and other newer physical channels and applications. A number of protocols and methods have been designed to account for and operate in particular applications, for example, voice-over IP, multimedia transport, satellite protocols, multicast protocols, and others. Although these various designs may provide certain advantages in particular applications, there continues a need for improved protocols and methods that account for wireless and similar networks that exhibit variable bandwidth and channel performance characteristics.
Particularly with wireless communications, conventional systems and methods, such as TCP/IP protocols, have several disadvantages. These disadvantages include high round trip times (RTT) of communications, variance in measurements in RTT because of channel characteristic variation, substantial packet loss, high bit error rates, false assumption that data loss because of congestion versus slow rate of sending, multichannel possibilities not anticipated, and ARQ techniques are often prohibitively expensive. Moreover, certain recent advances in technology, such as computer speeds and error correction techniques, can provide improvements, however, these advances have not previously been exploited to their potential.
In sum, there is a need for improvement in the art and technology of communications over low bandwidth, poor quality channels, such as wireless networks.
An embodiment of the invention is a method of communications over a network. The method includes the steps of packetizing a payload into a series of data packets, inserting header packets at the beginning, middle, and towards the end of the series, transmitting the series, together with the header packets, receiving at least some of the data packets of the series and at least one of the header packets, and sending an acknowledgement selected from the group consisting of: all data packets and at least one header packet received; not all data packets received and at least one header packet received; and some data packets received, but no header packet received.
In a further aspect, the method further includes the step of terminating the method if the acknowledgement is that all data packets and at least one header packet are received.
In another aspect, the method further includes the step of identifying the data packets not received if at least one header packet is received but not all data packets received. The acknowledgement of the step of sending includes identifiers of the data packets not received. The method also includes the step of re-transmitting only the data packets not received.
In a further aspect, the method includes the step of identifying that some data packets, but not any header packet, is received. The acknowledgement of the step of sending includes identifiers of the data packets received. The method also includes the steps of determining which data packets were not received, based on the identifiers in the acknowledgement and re-transmitting only the header packet and the data packets not received.